The influence of phosphorus and CO poisoning on Pd/SSZ-13 with different Al distributions as passive NOx adsorbers

Phosphorus and CO are typical poisonous substances under realistic working conditions for Pd/SSZ-13 passive NOx Adsorbers (PNA). In this research, the Pd/SSZ-13 with different Al distributions were subject to phosphorus and CO poisoning. The characterization results indicated the resistance to both P and CO increased with the amount of paired Al on SSZ-13 support. Paired Al facilitated the formation of Pd2+Z2 which was more stable against [Pd(OH)]+ under P poisoning. The Pd2+ preferred to transform to Pd+ after poisoning while the [Pd(OH)]+ was more likely turned to agglomerated Pd. The Al-Pd-Al structure also mitigated dealumination during P poisoning. On the other hand, paired Al promoted the ion-exchange of Pd on the SSZ-13 support and led to a more homogeneous Pd distribution. This effectively alleviated the Ostwald ripening and particle migration thus preserving the performance of the catalyst under CO atmosphere. This study provided a new perspective for designing PNA materials with high resistance.